Wireless LAN (Local Area Network) complying with the standards, such as IEEE 802.11, is in wide use in recent years. Such wireless LAN includes two kinds of network configurations. One is an infrastructure mode and the other is an ad-hoc mode. It further includes a network configuration called a wireless distribution system (WDS). The infrastructure mode is configured by a base station apparatus and terminal apparatuses located within a cell site, which is formed by said base station apparatus.
A network formed by combining a base station apparatus and a plurality of terminal apparatuses is called a basic service set (BSS). Generally, the base station apparatus, which connects to a wired backbone network, relays packet signals between the backbone network and the terminal apparatuses. Further, the base station apparatus also relays the packet signals between the terminal apparatuses. On the other hand, the ad-hoc mode does not include the base station apparatus and is configured by terminal apparatuses only. Generally, the terminal apparatuses do not have the function of relaying the packet signals but directly transmit the packet signals between them. Also, WDS relays the packet signals even between base station apparatuses (See Non-patent Document 1, for instance).